WO2020097559A2 - Réacteur à membrane d'hydrogel catalytique pour traitement de contaminants aqueux - Google Patents

Réacteur à membrane d'hydrogel catalytique pour traitement de contaminants aqueux Download PDF

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Publication number
WO2020097559A2
WO2020097559A2 PCT/US2019/060613 US2019060613W WO2020097559A2 WO 2020097559 A2 WO2020097559 A2 WO 2020097559A2 US 2019060613 W US2019060613 W US 2019060613W WO 2020097559 A2 WO2020097559 A2 WO 2020097559A2
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hydrogel
catalytic
hollow fiber
fiber membrane
alginate
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WO2020097559A3 (fr
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Kyle Doudrick
Robert Nerenberg
Randal MARKS
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University of Notre Dame
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University of Notre Dame
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Priority to US17/269,204 priority Critical patent/US11926545B2/en
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Publication of WO2020097559A3 publication Critical patent/WO2020097559A3/fr
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/70—Treatment of water, waste water, or sewage by reduction
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0081—After-treatment of organic or inorganic membranes
    • B01D67/0088—Physical treatment with compounds, e.g. swelling, coating or impregnation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/08—Hollow fibre membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/14—Dynamic membranes
    • B01D69/141—Heterogeneous membranes, e.g. containing dispersed material; Mixed matrix membranes
    • B01D69/145—Heterogeneous membranes, e.g. containing dispersed material; Mixed matrix membranes containing embedded catalysts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/024—Oxides
    • B01D71/027—Silicium oxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/44—Palladium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
    • B01J35/45—Nanoparticles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/04—Characteristic thickness
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/10—Catalysts being present on the surface of the membrane or in the pores
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/12—Halogens or halogen-containing compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/16—Nitrogen compounds, e.g. ammonia
    • C02F2101/163—Nitrates
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/16—Nitrogen compounds, e.g. ammonia
    • C02F2101/166—Nitrites
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/30—Organic compounds
    • C02F2101/36—Organic compounds containing halogen
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2305/00—Use of specific compounds during water treatment
    • C02F2305/08—Nanoparticles or nanotubes

Definitions

  • Heterogeneous hydrogenation catalysis is a reduction process for treating oxidized contaminants using hydrogen gas (H 2 ).
  • HHC hydrogenation catalysis
  • target reactions occur at the interface between solid (catalyst), liquid (water), and gas phases.
  • Palladium (Pd) is a catalyst for HHC due to high activity and desirable selectivity. While attempts have been made to replace Pd and other platinum group metals (PGMs) with more earth-abundant materials (e.g., metals sulfides and phosphides), their activities are orders of magnitude lower than PGMs, they are unstable in aqueous environments, and/or they require high operating pressures and temperatures. Although PGMs materials are costly, economic analysis has shown that recent advances in nanotechnology have made PGM catalysts cost competitive compared to other treatment technologies (e.g., ion exchange, air stripping, activated carbon adsorption). However, full-scale HHC implementation has yet to come to fruition due to mass transfer limitations, costs, catalyst instability, and scalability of current treatment options.
  • PGMs platinum group metals
  • Three-dimensional interfacial catalytic membranes may be used for immobilized catalyst reactors that allow for a dense loading of nano-sized catalysts and delivers Fh through a counter-diffusional pathway.
  • Membrane-type reactors have previously been demonstrated for hydrogenation reactions using alumina tubular membranes loaded with catalyst particles for NO2 reduction; ammonia selectivity was controlled through modification of Fh partial pressure within the reactor.
  • such reactors suffer from complex catalyst synthesis procedures, poor control of catalyst loading, and low contaminant reaction rates.
  • the scale-up of known reactors are limited by the challenge of immobilizing the catalyst while maintaining efficient mass transport and reaction kinetics.
  • the present disclosure provides a catalytic assembly comprising:
  • a hollow fiber membrane comprising an inner surface defining a channel and an outer surface, wherein the hollow fiber membrane is permeable to a gas;
  • a plurality of catalytic nanoparticles embedded in the reactive coating adapted to catalyze a reaction between the gas and the contaminant.
  • the present disclosure provides method of preparing a catalytic assembly, comprising:
  • a hollow fiber membrane into a first solution comprising alginate, wherein the hollow fiber member comprises an inner surface defining a channel and an outer surface; removing the hollow fiber membrane from the first solution, wherein the outer surface of the hollow fiber membrane is at least partially coated with an alginate solution coating;
  • the present disclosure provides method for water treatment, comprising
  • FIG 1 A is a graphic showing a representative catalytic hydrogel membrane unit as described herein.
  • FIG. 1B shows a representative preparation process for catalytic hydrogel film on a hollow fiber membrane (HFM).
  • a clean HFM is dipped in an aqueous solution of sodium alginate, then rapidly transferred to a solution of Pd(N03)2 and CaCb to cross-link.
  • Pd2+ ions are reduced in a sodium borohydride (NaBH 4 ) solution to form Pd nanoparticles.
  • NaBH 4 sodium borohydride
  • the coated membrane is then installed in a glass reactor for hydrogenation catalysis experiments.
  • FIGS. 2A-2D show representative results of characterization of a catalytic hydrogel membrane (CHM).
  • FIG. 2A shows TEM image of Pd nanoparticles isolated from hydrogel support.
  • FIG. 2B shows a histogram of particle diameters measured from TEM images showing a normal distribution.
  • FIG. 2C shows OCT cross-sectional image of hydrogel on HFM. The lower two white lines delineate the HFM wall, with the hydrogel above.
  • FIG. 2D shows SAED pattern of Pd nanoparticles isolated from a CHM.
  • FIG. 3 A shows a representative 8-membrane reactor assembly.
  • FIG. 3B shows a close-up view of individual CHMs installed into the membrane reactor assembly.
  • FIG. 4A shows a schematic of a reactor assembly for batch-recycle nitrite hydrogenation experiments.
  • FIG. 4B shows a schematic of a reactor configuration for continuous-recycle nitrite hydrogenation including eight HFM strands in reactor.
  • FIG. 5A shows a photograph of microsensor analysis of O2 concentrations.
  • Microsensor (glass needle) is inserted into reactor containing CHM.
  • the site of insertion is illuminated and the microsensor position, controlled by a micro-manipulator, is observed using the optical microscope in foreground.
  • FIG. 5B shows a configuration of a steady-state reactor assembly for microsensor analysis.
  • FIG. 6 shows Concentration profiles of 0 2 and H 2 during catalytic reduction of 0 2 by a CHM as measured by microsensors.
  • H 2 diffuses out of the HFM wall (left-side) and through the hydrogel (dotted region), while 0 2 passes from the aqueous region (right-side) through the hydrogel.
  • Reaction of H 2 and 0 2 at catalytic sites results in the formation of distinct regions given at top of figure.
  • NRZ non-reactive zone
  • RZ reactive zone
  • LDL liquid diffusion layer.
  • Dashed lines indicate estimated transition points between these regions and the solid line indicates the outer edge of catalytic hydrogel.
  • the dot at the HFM wall represents the saturation concentration of H 2 at room temperature, which is not achieved in the system due to mass transfer limitations on H 2 diffusion through the HFM wall.
  • FIGS. 7A and 7B shows microsensor profiles of O2 (FIG. 7A) and B) H2 (FIG. 7B) under inert conditions.
  • O2 measurements were taken with N2 in the HFM lumen.
  • H2 measurements were taken with N2 rapidly bubbling into the aqueous reservoir to displace O2.
  • FIG. 8 A shows kinetics of NO2 removal by a CHM containing 3.68 mg of Pd.
  • FIG. 8B shows rate constants of NO2 removal as function of total Pd embedded in the CHM. k is the observed rate constant and A:’is the Pd mass-normalized rate constant.
  • FIG. 9 shows a conceptual diagram of counter-diffusional H2 and NO2 transport in a CHM with a low Pd-loading density (top panel) and a high Pd-loading density (bottom panel).
  • the ratio of H2 to N2 throughout the hydrogel region is shown as a ratio of H2 to the total H2 + NO2 .
  • H2 and NO2 are shown in relative amounts varying from 0 to 1 (concentrations divided by their highest concentration at the hydrogel boundary). Shifts in RZ thickness are
  • FIG. 10A shows NH 4 + selectivity as a function of reaction time for CHMs with varying Pd-loadings.
  • the Pd mass (mg) for each sample is given in the legend.
  • FIG. 10B shows NH 4 + selectivity as a function of Pd-loading for each sample at approximately 25% NO2 conversion.
  • FIG. 11 shows conversion of NO2 in a groundwater in a continuous mixed flow reactor operated for 3 days.
  • the reactor included eight CHMs bundled together.
  • FIG. 12A shows a schematic of a catalytic hydrogel membrane reactor (CHMR) configuration including selected reactor parameters.
  • FIG. 12B shows a magnified schematic of a single CHM within the reactor showing the counter-diffusional delivery of NO 2 and H2 to the catalytic hydrogel.
  • CHMR catalytic hydrogel membrane reactor
  • FIG. 13 shows a representative continuous-flow operation of a CHMR under open, closed, and vented operation modes for H2 supply.
  • the hydraulic retention time was 40 min.
  • FIG. 14A shows batch removal of NO2 by recovered Pd nanoparticles suspended in aqueous solution with H2 (100 mL/min) and CO2 (150 mL/min).
  • FIG. 14B shows first order kinetics fit of NO2 removal by suspended catalyst particles.
  • FIGS. 15A-15E show representative results of N02- hydrogenation kinetic experiments.
  • the Pd-molarity normalized reaction rate (r') over a range of influent H2 percentages (in N2) as a function of effluent NO2 (i.e., steady-state) concentrations are presented for a 9.70 mg Pd-loaded CHMR (high loading, FIG. 15 A) and a 2.26 mg Pd-loaded CHMR (low loading, FIG. 15B).
  • the NO2 conversion for a range of influent Fh percentages (in N2) as a function of effluent NO2 concentrations are presented for a 9.70 mg Pd-loaded CHMR (FIG. 15C) and a 2.26 mg Pd-loaded CHMR (FIG. 15D).
  • FIG. 15E shows r' as a function of (mol-N bar-H2 mol -Pd 1 ).
  • the data was fit with a power-law by a minimizing RSS, with an R 2 value of 0.97.
  • FIGS. 16A and 16B show steady-state NH 4 + selectivity for NO2 hydrogenation over a range of initial NO2 concentrations and H2 percent mixtures for 9.7 mg Pd-loaded membrane (FIG. 16A) and 2.26 mg Pd-loaded membrane (FIG. 16B).
  • FIGS. 17A and 17B show a conceptual model of NO2 and H2 concentration profiles within a CHM. Concentration of NO2 and H2 as a function of position in the catalytic hydrogel is given over a range of conditions. Shaded boxes indicate the position of the R Z within the hydrogel. Beyond the hydrogel edge is the LDL and bulk aqueous regions (not shown).
  • FIG. 17A shows the effect of increased Hi% in the lumen while the influent NO2 concentration is held constant.
  • FIG. 17B shows the effect of increased NO2 concentrations while Hi% in the lumen is held constant.
  • FIGS. 18A-18C show a long-term continuous operation of a CHMR in the presence of known deactivation species 5 mg-S/L SO3 2' (FIG. 18 A), 1 mg-S/L HS (FIG. 18B), and 5 mg/L NOM (FIG. 18C).
  • the HS experiment was conducted in the absence CO2 to avoid acidic pH and the formation of H2S.
  • the vertical red dashed line represents the time point when the species was spiked into the influent reservoir.
  • FIG. 19 shows kinetics of NO2 removal by catalytic hydrogenation using CHM recovered Pd nanoparticles in a suspended catalyst batch reactor system with relevant catalyst deactivating species.
  • Left panel shows the results of NO2 only and in the presence of SO3 2' or DOM (CO2 bubbling, pH 5.8-6.3).
  • Right panel shows the results of NO2 only and in the presence of HS (no CO2 bubbling, pH 8.2-9.5).
  • FIGS 20A-20C show the effects of aqueous phase conditions on the structural stability of the Ca-alginate hydrogel.
  • FIG. 20 A shows the quantity of Ca 2+ released as a function of aqueous phase pH in Ca-alginate hydrogels with no Pd.
  • FIG. 20B shows the mass- ratio of Ca-alginate hydrogel after exposure to increasing total concentrations of monovalent, divalent, and mixed salt solutions.
  • FIG. 20C shows the mass-ratio of hydrogels over a 3-week period of exposure to ultrapure water and model groundwater. The error bars indicate the standard deviation of triplicate trials at the same condition.
  • catalytic assemblies having a hollow fiber membrane with a reactive coating and a plurality of catalytic nanoparticles embedded in the coating.
  • the assemblies may include a gas-permeable hollow fiber membrane coated with an alginate-based hydrogel containing catalyst nanoparticles.
  • the catalytic assemblies may be useful for catalyzing an interfacial reaction between a gas that permeates the membrane and the reactive coating and a chemical in a solution.
  • the assemblies may be useful for decontaminating water by catalyzing the reduction of a variety of contaminants.
  • the assemblies may be incorporated in a catalytic hydrogel membrane reactor, which benefit from counter- diffusional transport within the hydrogel, where the gas (e.g., H 2 ) diffuses from the interior of the membrane and contaminant species (e.g., NO2 , O2) diffuse from the bulk aqueous solution.
  • gas e.g., H 2
  • contaminant species e.g., NO2 , O2
  • the modifier“about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (for example, it includes at least the degree of error associated with the measurement of the particular quantity).
  • the modifier“about” should also be considered as disclosing the range defined by the absolute values of the two endpoints.
  • the expression“from about 2 to about 4” also discloses the range“from 2 to 4.”
  • the term“about” may refer to plus or minus 10% of the indicated number.
  • “about 10%” may indicate a range of 9% to 11%
  • “about 1” may mean from 0.9-1.1.
  • Other meanings of“about” may be apparent from the context, such as rounding off, so, for example “about 1” may also mean from 0.5 to 1.4.
  • alkane means a straight or branched chain saturated hydrocarbon.
  • alkane include, but are not limited to, methane, ethane, n-propane, isopropane, n-butane, isobutyl, n-pentane, n-hexane, n-heptane, n-octane, n-nonane, and n- decane.
  • aromatic compound means a compound having at least one aromatic group, such as an aryl group or a heteroaryl group.
  • aryl refers to a phenyl group or a fused aromatic ring system, such as indolyl, naphthyl, quinolinyl, and tetrahydroquinolinyl.
  • heteroaryl refers to an aromatic monocyclic ring or an aromatic fused ring system, which has at least one heteroatom independently selected from the group consisting of N, O and S.
  • halogen means a chlorine, bromine, iodine, or fluorine atom.
  • the term“contaminant” means to a chemical compound or molecule, or a group of compounds or molecules, present in water or an aqueous solution.
  • the contaminants may include undesired chemical species, such that the use and consumption of water containing such species are deemed to be harmful to an animal, such as a human.
  • the contaminants may include compounds or molecules that are poisonous to a human, cause a disease or disorder in a human, or generally threaten the health of a human.
  • each intervening number there between with the same degree of precision is explicitly contemplated.
  • the numbers 7 and 8 are contemplated in addition to 6 and 9, and for the range 6.0-7.0, the number 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, and 7.0 are explicitly contemplated
  • the present disclosure provides a catalytic assembly comprising:
  • a hollow fiber membrane comprising an inner surface defining a channel and an outer surface, wherein the hollow fiber membrane is permeable to a gas;
  • a plurality of catalytic nanoparticles embedded in the reactive coating adapted to catalyze a reaction between the gas and the contaminant.
  • the hollow fiber membrane allows a gas to permeate from one side to the other side of the membrane.
  • the hollow fiber membrane may be arranged, for example, in tubular shape having an inner surface and an outer surface.
  • the inner surface may define a void space, such as a channel, through which a gas may flow.
  • the hollow fiber membrane is arranged into a tube, the inner surface of which defining a channel, a gas is allowed to flow through the channel at a controllable pressure, and the gas permeates from the inner surface of the membrane to the outer surface of the membrane.
  • the hollow fiber membrane may include any suitable material that is permeable to a gas and does not interfere with the application of the reactive membrane.
  • the hollow fiber membrane comprises silicone, such as polydimethylsiloxane.
  • Commercially available materials suitable for the hollow fiber membrane include, for example, the RenaSilTM silicone rubber tubing supplied by Braintree Scientific, Inc (MA).
  • the hollow fiber membrane has an outer diameter of about 500 pm to about 2000 pm, including, but not limited to, about 500 pm to about 1500 pm, about 600 pm to about 1200 pm, about 600 pm to about 1000 pm, or about 800 pm to about 1000 pm. In some embodiments, the hollow fiber membrane has an inner diameter of about 250 pm to about 1000 pm, including, but not limited to, about 300 pm to about 1000 pm, about 400 pm to about 1000 pm, about 400 pm to about 800 pm, or about 500 pm to about 800 pm. In some embodiments, the hollow fiber membrane comprises silicone and has an outer diameter of about bout 600 pm to about 1200 pm and an inner diameter of about 400 pm to about 800 pm. In particular embodiments, hollow fiber membrane comprises silicone and has an outer diameter of about bout 800 pm to about 1000 pm and an inner diameter of about 500 pm to about 800 pm.
  • the reactive coating is applied to the outer surface of the hollow fiber membrane, and it is permeable to a gas and a contaminant in an aqueous solution (e.g., a chemical compound or molecule in water). In general, the reactive coating does not interfere with the reaction between the gas and the contaminant.
  • the reactive coating comprises a hydrogel.
  • the hydrogel may include a hydrophilic polymer that may be crosslinked to form a three- dimensional structure.
  • the reactive coating comprises a hydrogel, such as a hydrogel comprising alginate.
  • Suitable hydrogels include, for example, an alginate hydrogel crosslinked by a divalent cation (e.g., Ca 2+ , Ba 2+ , Sr 2+ ).
  • Suitable alginate include those having a low, medium, or high viscosity. In some embodiments, the alginate has a low or medium viscosity (e.g., about 40 mPa s to about 2000 mPa s).
  • suitable alginates may include products under CAS Reg. No. 9005-38-3.
  • the source of Ca 2+ may include, for example, CaCh, CaS0 4 , and/or CaCCh.
  • the reactive coating may have a thickness of about 10 pm to about 2,000 pm.
  • the thickness may be at least 10 pm, at least 50 pm, at least 100 pm, at least 200 pm, at least 500 pm, at least 1,000 pm, at least 1,500 pm, or at least 1,800 pm.
  • the thickness may be less than 2,000 pm, less than 1,800 pm, less than 1,500 pm, less than 1,000 pm, less than 500 pm, less than 200 pm, less than 100 pm, or less than 50 pm.
  • the thickness may be about 10 pm to about 1,000 pm, about 50 pm to about 1,000 pm, about 50 pm to about 500 pm, or about 50 pm to about 200 pm.
  • the thickness is about 50 pm to about 200 pm, including, for example, about 70 pm, about 90 pm, about 110 pm, about 130 pm, about 150 pm, or about 170 pm.
  • the thickness is about 150 pm.
  • the catalytic assembly include one or more layers of reactive coatings (e.g., hydrogels), each having a thickness as described herein, with a total thickness less than 2,000 pm, such as less than 1,500 pm or less than 1,000 pm.
  • reactive coatings e.g., hydrogels
  • the hollow fiber membrane and the reactive coating as described herein are permeable to a gas.
  • the hollow fiber membrane and the reactive coating are permeable to hydrogen (Fh).
  • the gas may be pure Fh or a gas mixture including Fh, in which case at least the Fh in the gas mixture permeates the hollow fiber membrane and the reactive coating.
  • the catalytic nanoparticles include one or more catalysts (such as metal catalysts), which can catalyze a chemical reaction.
  • the catalytic nanoparticles are embedded in the reactive coating (e.g., dispersed homogeneously in a hydrogel coating) and are adapted to catalyze a reaction between a gas (e.g., Fh) and a contaminant in an aqueous solution.
  • a gas e.g., Fh
  • the gas and contaminant permeate the reactive coating and the reaction between them may take place inside the reactive coating on the surface of the catalytic nanoparticles.
  • the catalytic nanoparticles have an average particle size of about 1.0 nm to about 10.0 nm.
  • the average particle size may be at least 1.0 nm, at least 2.0 nm, at least 3.0 nm, at least 4.0 nm, at least 5.0 nm, at least 6.0 nm, at least 7.0 nm, at least 8.0 nm, or at least 9.0 nm.
  • the average particle size may be less than 10.0 nm, less than 9.0 nm, less than 8.0 nm, less than 7.0 nm, less than 6.0 nm, less than 5.0 nm, less than 4.0 nm, less than 3.0 nm, or less than 1.0 nm.
  • the average particle size is about 1.0 nm to about 9.0 nm, about 2.0 nm to about 8.0 nm, about 3.0 nm to about 7.0 nm, or about 3.0 nm to about 6.0 nm. In particular embodiments, the average particle size is about 3.0 nm to about 6.0 nm, including, but not limited to, about 3.5 nm, about 4.0 nm, about 4.5 nm, about 5.0 nm, or about 5.5 nm.
  • the nanoparticles can catalyze a hydrogenation reaction.
  • the hydrogenation reaction may be, for example, a reaction between Th and a contaminant that permeate the reaction coating.
  • the catalytic nanoparticle comprises a metal catalyst, such as palladium (Pd), which can catalyze a reaction.
  • the catalytic nanoparticles include palladium as the catalyst.
  • the catalytic nanoparticles include palladium and at least one other nonmetal or metal as the catalyst.
  • the catalytic nanoparticles include palladium and at least one of indium (In) and rhenium (Re).
  • Suitable catalysts also include the Pd-based catalysts disclosed in Chaplin et al., ( Environ . Sci. Technol. , 2012, 46(7), 3655-3670), which is incorporated herein by reference in its entirety.
  • the catalytic assembly include alginate hydrogel as reactive coating and catalytic nanoparticles comprising palladium.
  • the dry weight ratio of palladium to the alginate is about 1 : 100 to about 20: 100.
  • the dry weight ratio may be at least 1 : 100, at least 5: 100; at least 10:100, at least 15: 100, or at least 18: 100.
  • the dry weight ratio may be less than 20:100, less than 15:100, less than 10: 100, less than 5: 100, or less than 2: 100.
  • the dry weight ratio is about 2: 100 to about 18:100, about 5: 100 to about 18: 100, about 5: 100 to about 15: 100, or about 5: 100 to about 10: 100.
  • the dry weight ratio is about 5:100 to about 10: 100, such as 5: 100, 6: 100, 7: 100, 8: 100, 9: 100, or 10: 100.
  • the contaminant permeating the reactive coating may undergo a reaction that results in reducing the amount of, or eliminating, the contaminant from an aqueous solution.
  • the compound may undergo a reduction reaction catalyzed by the catalytic nanoparticles described herein and be reduced by the gas (e.g., Th) permeating the reactive coating.
  • the nanoparticle may catalyzes H2 to form H atoms, which then that react with (e.g., reduce) the contaminant that is on the nanoparticle surface.
  • the reduction reaction may include any reaction that leads to a decrease in the oxidation state of an atom in the contaminant.
  • the reduction reaction may be a
  • hydrodehalogenation reaction in which at least on halogen atom in a halogenated organic compound is replaced by hydrogen; a hydrodeoxygenation reaction, in which the oxygen atoms in the oxyanion is removed by hydrogenation to water; or an N-N hydrogenolysis reaction, in which the N-N bond in a compound is converted to N-H bonds.
  • Compounds that may be reduced by a hydrodehalogenation reaction includes, but are not limited to, halogenated alkanes, such as carbon tetrachloride (CT), and l,2-dichloroethane; halogenated ethylenes, such as dichloroethylene (DCE), trichloroethylene (TCE), and perchloroethene (PCE); halogenated aromatic compounds, such as chlorinated benzenes, polychlorinated biphenyls (PCBs), and chlorinated phenols.
  • halogenated alkanes such as carbon tetrachloride (CT), and l,2-dichloroethane
  • halogenated ethylenes such as dichloroethylene (DCE), trichloroethylene (TCE), and perchloroethene (PCE)
  • halogenated aromatic compounds such as chlorinated benzenes, polychlorinated biphenyls (PCBs), and chlor
  • Compounds that may be reduced by a hydrodeoxygenation reaction includes, but are not limited to, nitrate (NCh ), nitrite (NO2 ), bromate (BrOf), chlorite (CIO2 ), chlorate (CIO3 ), perchlorate (Cl0 4 ) ⁇
  • NCh nitrate
  • NO2 nitrite
  • BrOf bromate
  • CIO2 chlorite
  • CIO3 chlorate
  • perchlorate Cl0 4
  • These compounds may have a counterion, such as sodium (Na + ) or calcium (Ca 2+ ) and other metal ions.
  • N-N hydrogenolysis reaction includes, but are not limited to, N-nitrosamines, such as N-nitrosodimethylamine (NDMA).
  • NDMA N-nitrosodimethylamine
  • PAHs polycyclic aromatic hydrocarbons
  • formate formate
  • carbonate carbonate
  • Chaplin et al. incorporated herein by reference
  • the compound permeating the reactive coating and reacting with the gas permeating the reactive coating is a halogenated alkane, a halogenated ethylene, a halogenated aromatic compound, a nitrate, a nitrite, a bromate, a chlorite, a chlorate, a perchlorate.
  • the compound is a nitrate, a nitrite, a bromate, a chlorite, a chlorate, or a perchlorate.
  • the compound is a nitrate.
  • the compound is a nitrite.
  • the contaminant comprises a halogenated alkane, a halogenated ethylene, a halogenated aromatic compound, a nitrate, a nitrite, a bromate, a chlorite, a chlorate, a perchlorate, or a combination thereof.
  • the contaminant comprises a nitrate, a nitrite, a bromate, a chlorite, a chlorate, or a perchlorate.
  • the contaminant comprises a nitrate.
  • the contaminant comprises a nitrite.
  • the catalytic nanoparticles include palladium and the contaminant comprises a nitrite (such as NaNCh). In some embodiments, the catalytic nanoparticles include palladium and indium and the compound comprises a nitrate (such as NaNCh). In some embodiments, the catalytic nanoparticles include palladium and rhenium, and the contaminant comprises a perchlorate (such as NaClCh).
  • a method of preparing a catalytic assembly as described herein includes:
  • the hollow fiber member comprises an inner surface defining a channel and an outer surface
  • the hollow fiber membrane may include the suitable materials as described herein.
  • the hollow fiber membrane include silicone.
  • the hollow fiber membrane is a silicone membrane available from a commercial supplier, and it is arranged into a tubular shape having an outer diameter of about 500 pm to about 2000 pm, and an inner diameter of about 250 pm to about 1000 pm.
  • the first solution provides alginate that can be crosslinked to for a hydrogel. When applied to the outer surface of the hollow fiber membrane, the crosslinded hydrogel forms a coating.
  • the first solution includes sodium alginate. Suitable sodium alginates include those commercially available products (CAS Reg. No. 9005-38-3), such as those supplied by Chem-Implex International Inc. (IL) (catalog No. 01469).
  • the first solution may be an aqueous solution prepared by dissolving sodium alginate in water at a concentration of about 1 wt% to about 5 wt% (weight sodium alginate/weight water). In some embodiments, the first solution was prepared by dissolve sodium alginate in ultrapure water (18.2 MW-cm) at a concentration of about 2 wt%.
  • the second solution includes Ca 2+ (such as CaCk) which causes formation of a crosslinked calcium-alginate hydrogel.
  • Suitable sources of Pd 2+ include, for example, palladium nitrate, such as palladium nitrate dihydrate (Pd(NCh)2 ⁇ 2H 2 0).
  • the second solution may be prepared by dissolving the Ca 2+ and Pd 2+ compounds in water to form an aqueous solution.
  • the concentration of Ca 2+ may be about 50 mM to about 200 mM.
  • the Ca 2+ concentration may be about 80 mM, about 100 mM, about 120 mM, about 150 mM, or about 180 mM.
  • the concentration of Ca 2+ is about 80 mM, about 100 mM, or about 120 mM.
  • the concentration of Pd 2+ may be in an appropriate range such that the final loading of Pd is about 1.0% to about 12.5% relative to the crosslinked alginate (weight Pd/dry weight of crosslinked alginate).
  • the loading of Pd relative to the crosslinked alginate may be about 5.0%, about 7.5%, or about 10.0%.
  • the loading of Pd relative to the crosslinked alginate is about 7.5%.
  • the second solution includes Ca 2+ and at least one other metal ion, such as salts of Ba 2+ or Sr 2+ .
  • the second solution includes Pd 2+ and at least one other metal capable of catalyzing the reaction as described herein.
  • the second solution may include Pd 2+ and at least one of indium (In) and rhenium (Re) salts.
  • the other metals may be applied by contacting the reactive coating (e.g., hydrogel) with a separate solution, whereupon the other metals are transferred into the reactive coating.
  • the hydrogel may be submerged in a solution containing In and/or Re salts, whereupon the In and/or Re ions diffuse into the coating.
  • the hydrogel loaded with In and/or Re ions may then react with NaBFU to reduce the ions (e.g., to In/Re).
  • the third solution include NaBFF, which reduces the Pd 2+ ions to form Pd nanoparticles embedded in the hydrogel coating.
  • the third solution may be prepared by dissolving NaBH4 in water to form an aqueous solution at a concentration of about 1.0 mM to about 5 mM.
  • the catalytic assembly prepared by the method described herein may be stored in ultrapure water until use.
  • HHC heterogeneous hydrogenation catalysis
  • CHM catalytic hydrogel membrane
  • the CHM may include, for example, a gas-permeable hollow-fiber membrane (HFM) coated with an alginate-based hydrogel containing catalyst nanoparticles.
  • HMF gas-permeable hollow-fiber membrane
  • the CHM operates using counter-diffusional transport of reactive species within the hydrogel, where a gas (e.g., hydrogen
  • H 2 diffuses from the interior of the membrane and dissolved target species (e.g., a dissolved contaminant) diffuse from the bulk aqueous solution.
  • Counter-diffusional delivery of H 2 reduces consumption of H 2 and allows the reaction to be“tuned” towards desired by-products.
  • the CHM reactor is the first to use hydrogels for catalyst immobilization in conjunction with counter-diffusional membrane techniques.
  • a CHM device is developed with a catalyst (Pd) and contaminants (e.g., NCte ).
  • the present disclosure (i) develops and physically characterizes a CHM with Pd nanoparticle catalysts, (ii) investigates the counter-diffusional behavior of the CHM using 0 2 as a model contaminant, (iii) provides a proof-of-concept study assessing the reduction of a water contaminant, N0 2 , as a function of Pd loading, (iv) demonstrates the effects of H 2 delivery mode and mass transport limitations on the activity and by-product selectivity of N0 2 reduction, and (v) establishes the short-term stability of the CHM reactor for reduction of N0 2 over a three-day period.
  • a method for water treatment comprising: contacting a catalytic assembly as described herein with a volume of water comprising a contaminant, whereupon the contaminant permeates into the reactive coating; and
  • the water has a pH between about 4.0 and about 9.0.
  • the pH may be at least 4.0, at least 5.0, at least 6.0, at least 7.0, or at least 8.0.
  • the pH may less than 9.0, less than 8.0, less than 7.0, less than 6.0, or less than 5.0.
  • the pH may about 4.5 to about8.5, about 4.5 to about 8.0, about 4.5 to about 7.5, about 4.5 to about 7.0, or about 4.5 to about 6.0.
  • the method described herein may be conducted under acidic condition (pH 7.0 or less) without dissolving the hydrogel.
  • the pH may be about 4.5 or even lower while the hydrogel structure is maintained.
  • the pH is about 4.5 to about 6.0.
  • the water may include any contaminant as described herein, or combinations thereof.
  • the concentrations of the contaminant is about 0.01 mM to about 2.0 mM, including, but not limited to about 0.05 mM, about 0.1 mM, about 0.15 mM, about 0.2 mM, about 0.5 mM, about 0.8 mM, about 1.0 mM, about 1.2 mM, about 1.5 mM, about 1.8 mM, or about 2.0 mM.
  • the reactive membrane has a thickness between about 10 pm and about 2,000 pm as described herein.
  • the thickness may be about 10 pm to about 1,000 pm, about 50 pm to about 1,000 pm, about 50 pm to about 500 pm, or about 50 pm to about 200 pm.
  • the thickness is about 50 pm to about 200 pm, including, for example, about 70 pm, about 90 pm, about 110 pm, about 130 pm, about 150 pm, or about 170 pm. In particular embodiments, the thickness is about 150 pm.
  • the gas is hydrogen. In the some embodiments, the gas is hydrogen at a pressure of about 1.0 psi to about 5.0 psi.
  • the pressure may be at least 1.0 psi, at least 2.0 psi, at least 3.0 psi, or at least 4.0 psi.
  • the pressure may be less than 5.0 psi, less than 4.0 psi, less than 3.0 psi, or less than 2.0 psi.
  • the pressure may be about 1.0 psi to about 4.5 psi, about 2.0 psi to about 4.5 psi, about 2.0 psi to about 4.0 psi, or about 2.0 psi to about 3.5 psi.
  • the pressure is about 2.0 psi to about 4.0 psi, such as about 2.5 psi, about 3.0 psi, or about 3.5 psi. In particular embodiments, the pressure is about 3.0 psi.
  • the catalytic nanoparticles include palladium. In some embodiments, the catalytic nanoparticles include palladium and at least one other metal capable of catalyzing the reaction as described herein.
  • the second solution may include palladium and at least one of indium and rhenium.
  • a representative CHM including a gas-permeable hollow fiber membrane (HFM) coated with an alginate-based hydrogel containing catalyst nanoparticles was prepared using a method involving in-situ reduction of Pd 2+ ions enmeshed in the hydrogel (FIG. 1B). Briefly, 2 wt% (weight of alginate/weight of water) alginic acid sodium salt (low viscosity, #01469, Chem- Implex Inc.) was dissolved in ultrapure water (18.2 MW-cm) with stirring until homogeneity was achieved. The alginate solution was transferred to a custom-built half-tube reactor for coating.
  • HAM gas-permeable hollow fiber membrane
  • a 20-mL cross- linking solution (100 mM total concentration) was prepared by dissolving calcium chloride (CaCb, anhydrous, #C77, Fisher Scientific) and palladium nitrate dihydrate (Pd(NCb)2 ⁇ 2H 2 0, #76070, Sigma Aldrich) in aqueous solution, which was then poured into a separate half-tube reactor.
  • the alginate-coated membrane was removed from the alginate solution and rapidly transferred to the Ca 2+ /Pd 2+ cross-linking solution.
  • the membrane was soaked in the cross- linking solution for 30 min to allow for complete cross-linking.
  • the resulting Ca-alginate hydrogel had a vibrant orange color from Pd 2+ intrusion.
  • the alginate coating and cross-link procedure was repeated once to increase the hydrogel thickness and stability.
  • the reduction of the embedded Pd 2+ to Pd nanoparticles was induced by submerging the membranes in 2.5 mM sodium borohydride (NaBH 4 , 98%, #13432, Alfa-Aesar), during which the hydrogel turned a dark gray color.
  • the completed catalytic hydrogel membrane was stored in ultrapure water until use.
  • Pd nanoparticles were extracted from the hydrogel by dissolving it in a solution of
  • ethylenediaminetetraacetic acid 0.1 M
  • sodium citrate 0.2 M
  • the isolated particles were then centrifugally washed and resuspended in ethanol. A drop of this solution was added to a transmission electron microscopy (TEM) grid, dried, and then analyzed by TEM (Titan 80-300, 300 kV) to obtain the primary particle size.
  • TEM transmission electron microscopy
  • SAED selected area electron diffraction
  • the total Pd mass loading in each CHM was determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES; Perkin- Elmer Optima 8000).
  • the hydrogel was first stripped from the HFM, dried in air at room temperature overnight, massed, and then digested in concentrated nitric acid (68%, redistilled, GFS) using microwave digestion (2l0oC for 45 min, 110 mL MarsXpress vessel, Mars6 Microwave Digester).
  • the color of the hydrogel of the CHM was dark grey and consistent throughout with no visible particles or aggregates.
  • OCT images (FIG. 2C) confirmed uniform dispersion of the Pd particles as no large aggregates were observed, and they showed the mean thickness of the hydrogel for a single-layer and double-layer coated HFM was 304 ⁇ 37 pm and 988 ⁇ 119 pm, respectively.
  • Longitudinal uniformity of Pd was investigated by analyzing the Pd-loading for 10 equivalent 2.5 cm segments of a single CHM. The Pd-loading was found to be consistent with an average Pd mass of 0.184 ⁇ 0.0206 mg for one segment.
  • Representative CHMR assembly was constructed by installing CHM of Example 1 in a tubular glass reactor with ports for aqueous and gaseous supplies (FIGS. 3 A and 3B).
  • CHM catalytic hydrogel membrane
  • Plastic T-connectors were installed on both ends of the tubing and the uncoated HFM ends of the CHMs were fixed in place with adhesive (urethane, #2RUD4, Grainger) to create a water-tight seal. Special care was taken to ensure the HFM openings were not crimped or sealed.
  • the CHM was installed in a tubular glass reactor with ports for aqueous and gaseous supplies, which formed the CHM reactor assembly (FIG. 4A).
  • the aqueous solution was composed of ultrapure water (18.2 MW-cm) and 0.35 mM of sodium nitrite (NaN0 2 , reagent grade, #0535, VWR).
  • 100% H 2 (ultra-high purity, #HY UHPT, American Gas and Welding) was supplied through the lumen of the HFM (operated in closed mode, constant lumen pressure of 3 psi).
  • a completely mixed flow reactor was assembled by bundling eight CHMs (7.5% theoretical Pd wt./dry alginate wt.) in a single reactor vessel (FIG. 4B).
  • the total volume of the reactor was 120 mL, and the influent/effluent flow rate was 1 mL/min.
  • the reservoir volume was recycled through the reactor at a rate of 60 mL/min to ensure that the reaction volume was well-mixed. 100% H 2 was supplied to the lumen at 3 psi in closed mode.
  • the reactor was operated continuously over a period of three days and reached steady-state within 6 hours.
  • the aqueous solution was recycled through the reactor at a flow velocity of 2.7 cm s 1 . Prior to analysis the system was operated for 0.5 hr to obtain steady-state conditions. As a control, in separate experiments, 100% N2 (high purity, #NI-300-HP, American Gas and Welding) was bubbled either into the lumen or the aqueous solution.
  • H2 and O2 microscale electrodes, or microsensors, with a 25-pm tip diameter were used to measure the dissolved H2 and O2 profiles within the catalytic hydrogel.
  • Microsensors were calibrated according to manufacturer’s instructions, and data was collected using Unisense Logger 2.7 software.
  • the microsensors, controlled with a motorized micro-manipulator (Model MC-232 and MM33, Unisense A/S), were inserted into the catalytic hydrogel perpendicular to the membrane until contact was established with the outer wall of the HFM. Measurements of species concentrations were then taken at 20-pm intervals as the microsensors were withdrawn through the hydrogel.
  • the concentration profiles of O2 and H2 in a CHM as measured by the microsensor are shown in FIG. 6. These profiles illustrate the concentrations of each species through the depth of the hydrogel and into the bulk aqueous zone. Distinct regions within the reactor were observed: the bulk aqueous region, the liquid diffusion layer (LDL), the reactive zone (RZ) of the hydrogel, and the non-reactive zone (NRZ) of the hydrogel. This bulk aqueous region is dominated by the flow of water parallel to the membrane and maintains a high oxygen concentration due to rapid recirculation of oxygenated water (e.g., 2.7 cm s 1 ) from the reservoir, while the bulk H2 concentrations approached zero.
  • LDL liquid diffusion layer
  • RZ reactive zone
  • NRZ non-reactive zone
  • aqueous species concentrations vary in a linear fashion per Fick’s First Law of diffusion.
  • the position of the inner edge of the LDL was determined through visual observation of the microsensor exiting the hydrogel, while the outer edge was determined empirically by evaluation of the position of the change in slope of the O2 concentration gradient. LDL thickness was found to be approximately 100 pm under the tested conditions. After diffusion through the LDL, O2 reaches the hydrogel surface.
  • the exterior region of the hydrogel closest to the LDL is the RZ, where Lh and O2 are reacting at catalyst sites.
  • the diffusivity of dissolved O2 in the CHM is greater than reported for other common supports, such as alumina (3.2 xlO 6 cm 2 /s) and activated carbon (0.58 xlO 6 cm 2 /s).
  • the effective diffusivity within the CHM may be improved by changing the alginate properties (e.g., viscosity, density).
  • the Pd-loading in a single CHM was varied from 0.128 to 3.68 mg, corresponding to theoretical Pd wt./dry alginate wt. loadings of 0.5% to 12.5%. The homogeneity of the Pd-loading was assumed to be consistent across samples.
  • the smaller RZ results in a faster k because internal diffusion effects are minimized, but it reduces the Pd mole-normalized rate ⁇ k’) since less Pd is being used within the hydrogel (i.e., only Pd near the bulk solution). Because diffusion within the hydrogel is progressively irrelevant with increasing Pd-loadings, k’ eventually levels off and becomes strictly governed by the inherent reaction rate of the catalyst.
  • the RZ is responsive to bulk concentrations of Fh and NO2 , and Pd-loading, and therefore may be manipulated by adjustment of any of these parameters, which may change observed kinetics as conditions within the RZ vary.
  • By-product selectivity is an outcome for evaluating the efficacy of the catalytic treatment of contaminants in water, and it can be used to further characterize the CHM.
  • NH 4 + forms selectively when the H/N ratio at catalytic active sites is high.
  • the NH 4 + selectivity declined with increasing Pd-loading and increased with reaction time for all samples.
  • the NH 4 + selectivity increased with reaction time because the H/N ratio increased as N was depleted (FIG. 10A).
  • Selectivity can also be altered by pH changes during the reaction. Due to the low initial NO2 concentrations and relatively low conversions ( ⁇ 30%), minimal pH shifts were observed (DrH ⁇ 1).
  • the normalized first-order rate constants ⁇ k’) for the counter-diffusional CHM, co- diffusional CHM, and co-diffusional suspension were 0.130, 0.168, and 0.180 L mol-Pd 1 s 1 , respectively. From these results, an activity ratio was calculated to highlight mass transfer limitations by the hydrogel and co-diffusional H delivery.
  • the activity ratio is defined herein as the ratio between the reaction rate of the supported catalysts to the suspended catalysts (e.g., counter-diffusional/suspended).
  • the activity ratios were calculated to be 0.72 and 0.93 for counter-diffusion and co-diffusion systems, respectively.
  • Another benefit of the counter-diffusional system the ability to control the amount of Fh that reaches the RZ.
  • changing the H/N ratio at reactive sites greatly affects the by-product selectivity.
  • the NH 4 + selectivity was 42%, 77%, and 92% for counter-diffusional, co-diffusional, and suspended catalyst systems, respectively.
  • Supplying Fh through the lumen allows control of the amount that reaches RZ since Fh must diffuse through the hydrogel toward the bulk solution.
  • the counter-diffusional system resulted in a lower H/N ratio and thus a lower NH 4 + selectivity.
  • the overall percent removal of NO2 was 30% after 1 day, 31% after 2 days, and 29% after 3 days.
  • the rate constant for NO2 was determined to be 0.073 L mol-Pd 1 s 1 , which is
  • immobilized counter-diffusional and suspended batch operation (activity ratio 0.54-0.72) further compares favorably to other immobilized systems, where greater reductions in activity have been reported by particle immobilization.
  • the CHMR was configured as a continuous-flow reactor with recycle (FIGS. 12A and 12B).
  • NO2 was added to the influent reservoir (1000 mL) at varying concentrations.
  • the reactor pH was buffered (5.8 to 6.3) by bubbling carbon dioxide (CO2, #CD75, American Gas and Welding) at 100 mL/min and by addition of 10 mM sodium bicarbonate (NaHCCb, ACS grade, #41900068-1, bio-world) into the influent reservoir.
  • CO2, #CD75 American Gas and Welding
  • NaHCCb sodium bicarbonate
  • 1.4 mM calcium chloride CaCb, anhydrous, C77-500, Fisher Scientific
  • the influent reservoir was fed to a reactor reservoir (120 mL) by a peristaltic pump (3 mL/min).
  • the reactor reservoir had two outlets.
  • the first outlet led to the CHMR and this was recycled through the CHMR and back into the reactor reservoir using a peristaltic pump (60 mL/min, liquid velocity 2.4 cm s 1 ).
  • the flowrate was chosen to establish a recycle ratio of 20 so the overall behavior of the system was comparable to a completely stirred reactor.
  • the second outlet was the system effluent (at water level) and the flowrate matched the influent flowrate (3 mL/min), creating a hydraulic retention time in the combined CHMR and reactor reservoir of 40 min.
  • the H2 flowrate in open mode was measured to be approximately 4 L min 1 at 3 psig.
  • the valve was closed to prevent the escape of H2 from the lumen end, so H2 could only leave by diffusing through the HFM wall.
  • the valve was opened every 15 min for 5 s.
  • H2 delivery can be achieved through different modes that will influence the H2 concentration in the catalytic hydrogel and H2 consumption efficiency.
  • the HFM In the“closed mode,” the HFM is sealed at the end and all H 2 that enters can only leave by diffusion through the HFM wall. H 2 consumption efficiencies in this mode approach 100% since all H 2 must pass into the catalytic hydrogel where reaction occurs.
  • the drawback to closed mode is back-diffusion of non-reactive gases (i.e., C0 2, N 2 ) from the aqueous phase into the sealed membrane. Back-diffusion results in an H 2 gradient along the lumen length (i.e., lower H 2 at one end), and therefore in the hydrogel, which lowers the catalytic activity of the CHMR.
  • the HFM In the“open mode,” the HFM is open at the end, and all the H 2 that does not diffuse through the HFM wall exits the HFM into the atmosphere. This mode is used to prevent formation of the unwanted H 2 gradients, and it improves catalytic activity, but causes a low H 2 consumption efficiency.
  • the final option is a mixture of closed and open modes, called“vented mode,” in which the HFM is set up similar to closed mode, but a valve is placed at the end of the HFM to allow it to be opened at regular intervals to flush out the inert gases. This maintains a consistent H 2 partial pressure throughout the HFM while ensuring good H 2 consumption efficiency.
  • a conservative vent cycle of 15 min closed followed by 5 s open was selected to maximize activity, limit H 2 gradient formation in the lumen, and allow pseudo-steady state conditions to develop in the CHMR.
  • the H 2 consumption efficiency can be determined by evaluating the ratio of H 2 consumed by reaction with N0 2 to the total volume released from the supplying tank during the reaction period. During a l-hr steady-state period, approximately 0.039, 0.62, and 0.54 mmol of H 2 were consumed by the reaction in closed, open, and vented modes, respectively. In the closed mode, the H 2 consumption efficiency approached 100% because all H 2 was assumed to leave the lumen only by diffusion. In open mode, most of the H 2 was released to the atmosphere (-9809 mmol/hr), so a low consumption efficiency of 0.0064% was observed.
  • r' is the reaction rate normalized to Pd molarity (i.e., mol-N mol-Pd 1 s 1 ) and is obtained from the from the steady-state continuous-flow experiments (Table 7). For all conditions, r' increased with increasing Fh and NO2 concentrations, and r' for the low Pd loading was higher at all conditions compared to the high Pd loading. Because the curve slopes are not linear and different rates were observed for the Fh variations under similar conditions, this indicates that the overall reaction rate is not strictly first-order and the rate will be dependent on the number of active Pd sites, the concentration of Fh, and the NO2 concentration.
  • FIG. 15E shows the r' for all conditions tested in this study as a function of (mol-N bar-Fh mol-Pd 1 ).
  • the activity ratio is a measure the loss of activity in the CHMR because of mass transfer limitations, calculated by dividing U'CHMR by k'tatch.
  • the ki ' for the low and high Pd loadings of the CHMR were 1.32 and 0.667 L mol -Pd 1 s l , respectively.
  • the ki ' for equivalent low and high loadings was 1.40 and 1.08 mol-Pd 1 s 1 , respectively.
  • the activity ratio for the low and higher loading was 0.94 and 0.62, respectively. This confirms the role of mass transport in limiting the reaction rates, especially in the case of the high loading, where the reactive zone was small and confined near the bulk solution.
  • the model When supplied with influent NO2 concentrations and H2 partial pressure in the lumen, the model predicts NO2 removal at steady state and the concentration profiles of reactive species within the hydrogel.
  • the location and thickness of the reactive zone (RZ; region of the catalytic hydrogel where H2 and NO2 interact at active catalyst active sites) can be estimated using the model and related to observed reaction kinetics.
  • the model considers diffusion of H2 from the lumen through the HFM wall and into the hydrogel, diffusion of NO2 from the bulk aqueous zone through the stagnant LDL and into the hydrogel, and the catalytic reaction of NO2 and H2 in the RZ.
  • a l-D model was constructed in AQUASIM, a water treatment simulation software that allows for linked reactor compartments to be analyzed together.
  • the model itself is based off of previous work and incorporates a“biofilm” compartment that includes the hydrogel and bulk aqueous regions, which are connected by a liquid diffusion layer.
  • the catalytic hydrogel can be considered a simple biofilm that is not affected by growth or decay processes.
  • H2 supply is modeled using a completely mixed compartment containing only H2 diffusively linked to the base of the hydrogel.
  • the l-D model solves for concentrations of NO2 and H2 based on the equation and diffusion effects as described previously. By-product formation and the effect of pH was not evaluated in this model.
  • a complete account of reactor conditions and constants used in the model is given in Table 6. Reactor configuration constants were selected to maintain
  • Influent NO2 is 1.78 mol-N m 3 (mmol L 1 ) and the lumen H2 pressure is a constant 1.2 atm, equivalent to open mode operation of a reactor at 3 psig.
  • the area of the membrane is given according to the surface area of 8 strands. This model does not take cylindrical 3D structure into account.
  • Pd loading is given as a density that is equivalent to densities measured in previous work, while hydrogel and liquid diffusifon layer thickness are taken from previous OCT and microsensor work, respectively.
  • FIGS. 17A and 17B show the model output of the concentration profiles of NO2 and H2 at steady-state conditions.
  • H2 diffuses from the HFM wall into the hydrogel, where a concentration profile develops that is dependent on both diffusive transport and catalytic reaction.
  • a similar, but counter-diffusional, profile develops for NO2 , as it diffuses from the bulk through the LDL and into the hydrogel, where it is also subject to both reaction and diffusion processes.
  • the concentration profile shape of both NO2 and H2 within the hydrogel change (FIG. 17A). At the lowest H2 partial pressures, H2 is rapidly consumed by reaction as it leaves the HFM wall and travels into the hydrogel.
  • the RZ (gray region) is made up of only a small fraction of the portion of the hydrogel nearest the HFM wall. NO2 fully penetrates the hydrogel and the NO2 concentration within the hydrogel is relatively constant, suggesting low catalytic reaction rates and confirms the low NO2 removal rates observed experimentally. As H2 concentrations increase, H2 penetrates deeper into the hydrogel towards the bulk before it is completely consumed by reaction with NO2 . The increased presence of H2 throughout the membrane generates increased reaction rate, causing an increase in the NO2 concentration gradient as NO2 is more rapidly consumed. Further, the RZ expands and shifts towards the hydrogel exterior as the H2 partial pressure increases, decreasing the average diffusive transport distance for NO2 before reaction.
  • the diffusive transport distance for NO2 to enter the RZ is minimized and NO2 reaction rates are maximized.
  • the observed concentration profile changes with increasing reactive species concentrations correlate well with the shifts in experimentally measured r' with changes in reactive species concentration.
  • EDTA ethylenediaminetetraacetic acid
  • sodium citrate 0.2 M
  • Pd nanoparticles (1.13 and 4.87 mg) were suspended in a 60-mL solution containing NaNCh (1.78 mM), NaHCCb (10 mM), and CaCb (1.4 mM). CO2 (100 mL/min) and H2 (150 mL/min) were bubbled continuously into the reactor. Pd masses similar to those used in the CHMR experiments (low and high loadings) were used. Periodic aqueous samples were taken, filtered, and then the NO2 and MLf concentrations were analyzed using IC. All batch experiments were repeated using 1.13 mg Pd in the presence of the deactivating species.
  • Pd nanoparticles (1.13 mg) were dispersed in a 60-mL solution containing sodium bicarbonate (10 mM) and CaCb (1.4 mM) and either Na2SCb (5 mg-S/L), SRNOM (5 mg/L) or Na2S (1 mg-S/L). CO2 bubbling (100 ml/min) was used again for Na2SCb and SRNOM, but not Na2S to avoid formation of LbS.
  • the Pd nanoparticles were stirred with Lb bubbling (150 mL/min) for 1 hour prior to addition of 0.6 mL of 178 mM NaN02 to bring initial NO2 concentration to 1.78 mM. Samples were taken hourly for analysis by IC.
  • concentrations of Ca 2+ and Pd in aqueous solution and the CHM mass were used as metrics for evaluating the stability.
  • the change in the CHM mass is reported as a mass ratio, equal to the CHM wet mass in ultrapure water (at equilibrium) divided by the CHM wet mass after being exposed to selected aqueous conditions for 7 d.
  • the mass ratio indicates swelling or contraction of the hydrogel structure due to changes in the total number of crosslinked sites.
  • the conditions evaluated in the 7 d experiments were: 0.5, 5, and 50 mM total concentration of either NaCl, CaCb, or NaCl + CaCb (10: 1.4 molar ratio). Additional hydrogel stability experiments were conducted by exposing the CHM to a hard groundwater for 21 d and comparing the results to ultrapure water.
  • FIGS. 20A-20C show the stability of hydrogels coated on HFMs or a range of aqueous conditions relevant to water treatment.
  • the groundwater also contained 1.25 mM Mg 2+ and this may have contributed to the crosslinking, although the affinity of alginate cross-link sites for Mg 2+ is lower than Ca 2+ .
  • Source waters with high concentrations of monovalent cations and low concentrations of divalent cations may need pretreatment (addition of Ca 2+ salts) before the CHMR due to the expansion and degradation of the Ca-alginate hydrogel.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Catalysts (AREA)

Abstract

La présente invention concerne des ensembles catalytiques qui comprennent : une membrane à fibres creuses perméable à un gaz ; un revêtement réactif perméable au gaz et à un contaminant ; et une pluralité de nanoparticules catalytiques incorporées dans le revêtement réactif et adaptées pour catalyser une réaction entre le gaz et le contaminant. La présente invention concerne en outre des procédés de préparation des ensembles catalytiques et leur utilisation pour traiter des eaux contaminées.
PCT/US2019/060613 2018-11-08 2019-11-08 Réacteur à membrane d'hydrogel catalytique pour traitement de contaminants aqueux Ceased WO2020097559A2 (fr)

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WO1990006996A1 (fr) 1988-12-19 1990-06-28 Sepracor, Inc. Procede et appareil de confinement de catalyseurs dans des systemes de reactions multi-phase par membranes
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WO1993017790A1 (fr) * 1992-03-13 1993-09-16 Solvay Umweltchemie Gmbh Catalyseur a support resistant a l'abrasion
US6054142A (en) * 1996-08-01 2000-04-25 Cyto Therapeutics, Inc. Biocompatible devices with foam scaffolds
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DE10064622B4 (de) 2000-12-22 2006-03-30 Venezia Tecnologie S.P.A., Porto Marghera Verfahren und katalytischer Kontaktor zur Entfernung von Nitrat, Nitrit, Perchlorat und anderen schädlichen Verbindungen aus verunreinigtem Wasser durch Wasserstoff
CN102170954A (zh) * 2008-07-31 2011-08-31 诺维信公司 用于二氧化碳提取的模块化膜反应器和方法
WO2012057701A1 (fr) * 2010-10-25 2012-05-03 Agency For Science, Technology And Research Membrane tubulaire fibreuse à enveloppe nanoporeuse
PL2718416T3 (pl) * 2011-06-06 2020-05-18 ReGenesys BVBA Namnażanie komórek macierzystych w bioreaktorach włóknisto-kapilarnych
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